阅读说明：本技术 一种钠离子电池负极材料及其制备方法 (Sodium-ion battery negative electrode material and preparation method thereof ) 是由 陈建 卿龙 李�瑞 岳晨曦 唐利平 于 2021-08-17 设计创作，主要内容包括：本发明公开了一种钠离子电池负极材料及其制备方法,该制备方法采用化学气相沉积法在低温下制备得到螺旋纳米碳纤维,然后依次对螺旋纳米碳纤维进行碳化、酸化,最后将钼源、硫源和酸化后的螺旋纳米碳纤维混合,然后置于反应釜内进行水热反应,然后离心、冷冻干燥、退火即得到所述钠离子电池负极材料。该方法制备得到的钠离子电池负极材料具有良好的导电性和循环稳定性。(The invention discloses a sodium ion battery cathode material and a preparation method thereof, wherein the preparation method comprises the steps of preparing spiral carbon nanofibers at a low temperature by adopting a chemical vapor deposition method, then sequentially carbonizing and acidifying the spiral carbon nanofibers, finally mixing a molybdenum source, a sulfur source and the acidified spiral carbon nanofibers, then placing the mixture in a reaction kettle for hydrothermal reaction, and then centrifuging, freeze-drying and annealing to obtain the sodium ion battery cathode material. The sodium ion battery cathode material prepared by the method has good conductivity and cycling stability.)

1. The preparation method of the negative electrode material of the sodium-ion battery is characterized by comprising the following steps of:

(1) preparing spiral nano carbon fibers: placing the catalyst in a tubular furnace, introducing protective gas, heating to 260-300 ℃ under the protective gas, stopping introducing the protective gas, introducing acetylene gas, reacting for 1-2 hours at a constant temperature, stopping introducing the acetylene gas, and introducing the protective gas until the temperature is cooled to room temperature to obtain the spiral carbon nanofibers;

(2) carbonizing: placing the spiral carbon nanofibers obtained in the step (1) in a tube furnace, heating to 600-800 ℃ under protective gas, and then carrying out heat preservation reaction for 1-5 hours to obtain carbonized spiral carbon nanofibers;

(3) acidifying: acidifying the carbonized spiral carbon nanofibers obtained in the step (2) with strong acid, filtering and washing the acidified spiral carbon nanofibers to be neutral after acidifying for 1-4 hours, and then freeze-drying the acidified spiral carbon nanofibers to obtain acidified spiral carbon nanofibers;

(4) grafting: and (3) sequentially adding a molybdenum source and a sulfur source into the acidified spiral carbon nanofibers obtained in the step (3), uniformly stirring, then placing in a reaction kettle for hydrothermal reaction, then centrifuging, freeze-drying, finally placing in a tubular furnace, heating to 500-600 ℃ under protective gas, and preserving heat for 1-5 hours to obtain the sodium ion battery cathode material.

2. The method for preparing the negative electrode material of the sodium-ion battery according to claim 1, wherein the catalyst is one or two of copper tartrate and ferrous tartrate.

3. The preparation method of the sodium-ion battery cathode material according to claim 1, wherein the introduction rate of acetylene gas is 70-120 mL/min.

4. The preparation method of the negative electrode material for the sodium-ion battery, according to claim 1, is characterized in that the heat preservation temperature in the step (1) is 280-300 ℃.

5. The method for preparing the negative electrode material of the sodium-ion battery according to claim 1, wherein the strong acid is one of concentrated nitric acid, concentrated sulfuric acid or concentrated hydrochloric acid.

6. The method for preparing the negative electrode material of the sodium-ion battery according to claim 1, wherein the washing in the step (3) is repeated by using distilled water and ethanol.

7. The method for preparing the anode material of the sodium-ion battery as claimed in claim 1, wherein the molybdenum source is one of ammonium molybdate, sodium molybdate and sodium molybdate; the sulfur source is one of thiourea and ammonium thioacetate.

8. The preparation method of the sodium-ion battery anode material according to claim 1, wherein the mass ratio of the molybdenum source to the sulfur source to the acidified spiral carbon nanofibers in step (4) is 1: 3-15: 0.1 to 5.

9. The preparation method of the negative electrode material of the sodium-ion battery as claimed in claim 1, wherein the hydrothermal reaction is carried out by heating to 270-300 ℃ and then carrying out a heat preservation reaction for 15-30 h.

10. The negative electrode material of the sodium-ion battery is characterized by being prepared by the preparation method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of sodium ion batteries, and particularly relates to a sodium ion battery cathode material and a preparation method thereof.

Background

Because of the increasing shortage of non-renewable energy sources such as petroleum, and the pollution of tail gas generated by burning petroleum to the environment is becoming serious. Researchers in various countries around the world are looking for new energy devices that clean energy and utilize energy more efficiently. Lithium ion batteries have gained rapid development as high specific energy battery systems in the fields of portable electronic products, electric tools, and electric vehicles. However, the development of large-scale energy storage power sources may not be supported due to the limitation of lithium resources. Therefore, an advanced battery system with abundant development resources and low cost is a necessary way for solving the future large-scale electricity storage application. The sodium element and the lithium are in the same main group, the chemical properties are similar, the electrode potential is relatively close, the sodium resource is rich, and the refining cost is low. If sodium is used for replacing lithium, the sodium ion battery with excellent working performance is developed, and the competitive advantage is greater than that of the lithium ion battery. Therefore, the search for sodium storage electrode materials with high capacity and excellent cycle performance has become a research hotspot in the battery field at present.

Molybdenum disulfide materials are considered as the most potential next generation sodium ion battery negative electrode materials due to their very high theoretical specific capacity, and therefore attract a great deal of research attention. But molybdenum disulfide materials have poor conductivity and expand too much in volume during charge and discharge, resulting in poor cycling stability and rate capability. In order to improve the structural stability and the electrical conductivity of molybdenum disulfide, many researchers compound carbon materials, such as porous carbon, carbon nanotubes, carbon microspheres, graphene and the like, with molybdenum disulfide, and the cyclic stability of molybdenum disulfide is remarkably improved.

The spiral carbon nanofiber has heat resistance, chemical stability, thermal expansibility and low density of common carbonaceous materials, and is widely applied to the fields of electrode materials, hydrogen storage materials, wave-absorbing materials, high-performance reinforced composite materials and the like due to the fact that a special spiral structure of the spiral carbon nanofiber has typical chiral characteristics and good elasticity.

Then, how to compound the spiral nano carbon fiber and the molybdenum disulfide to obtain the sodium ion battery cathode material with high conductivity and good cycling stability is a technical problem which is expected to be solved by the technical personnel in the field.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a sodium-ion battery negative electrode material and a preparation method thereof, and the sodium-ion battery negative electrode material with high conductivity and good cycling stability can be prepared by the preparation method.

The technical scheme of the invention is realized as follows:

a preparation method of a sodium-ion battery negative electrode material comprises the following steps:

(1) preparing spiral nano carbon fibers: placing the catalyst in a tubular furnace, introducing protective gas, heating to 260-300 ℃ under the protective gas, stopping introducing the protective gas, introducing acetylene gas, reacting for 1-2 hours at a constant temperature, stopping introducing the acetylene gas, and introducing the protective gas until the temperature is cooled to room temperature to obtain the spiral carbon nanofibers;

(2) carbonizing: placing the spiral carbon nanofibers obtained in the step (1) in a tube furnace, heating to 600-800 ℃ under protective gas, and then carrying out heat preservation reaction for 1-5 hours to obtain carbonized spiral carbon nanofibers;

(3) acidifying: acidifying the carbonized spiral carbon nanofibers obtained in the step (2) with strong acid, filtering and washing the acidified spiral carbon nanofibers to be neutral after acidifying for 1-4 hours, and then freeze-drying the acidified spiral carbon nanofibers to obtain acidified spiral carbon nanofibers;

(4) grafting: and (3) sequentially adding a molybdenum source and a sulfur source into the acidified spiral carbon nanofibers obtained in the step (3), uniformly stirring, then placing in a reaction kettle for hydrothermal reaction, then centrifuging, freeze-drying, finally placing in a tubular furnace, heating to 500-600 ℃ under protective gas, and preserving heat for 1-5 hours to obtain the sodium ion battery cathode material.

Further, the catalyst is one or two of copper tartrate and ferrous tartrate.

Further, the feeding rate of the acetylene gas is 70-120 mL/min.

Further, the heat preservation temperature in the step (1) is 280-300 ℃.

Further, the strong acid is one of concentrated nitric acid, concentrated sulfuric acid or concentrated hydrochloric acid.

Further, washing with distilled water and ethanol is repeated in step (3).

Further, the molybdenum source is one of ammonium molybdate, sodium molybdate and sodium molybdate; the sulfur source is one of thiourea and ammonium thioacetate.

Further, in the step (4), the mass ratio of the molybdenum source to the sulfur source to the acidified spiral carbon nanofibers is 1: 3-15: 0.1 to 5.

Further, the hydrothermal reaction is carried out by heating to 270-300 ℃, and then carrying out heat preservation reaction for 15-30 h.

The preparation method is adopted to prepare the negative electrode material of the sodium-ion battery.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention adopts the chemical vapor deposition method to prepare the spiral carbon nanofibers under the low temperature condition, and has low energy consumption, low cost and simple process. And the catalyst is directly fed into the tubular furnace for reaction, so that the processes of impregnation and heat treatment are not needed, the time is saved, the cost is reduced, and meanwhile, flammable and explosive hydrogen is not needed for reduction, so that the safety is ensured.

2. The spiral carbon nanofiber prepared by the method has a strong spiral structure, is high in spiral degree, has a three-dimensional conductive network structure, and is beneficial to subsequent constraint of molybdenum disulfide (MoS)₂) And the method is favorable for limiting the volume expansion of the spiral nano carbon fiber/molybdenum disulfide composite material in the circulation process, and the conductivity, the circulation stability and the electrochemical stability of the composite material are improved. Meanwhile, the prepared spiral carbon nanofiber has the diameter of only about 100 nm, has a high specific surface area and can store more Na⁺Thereby being beneficial to improving the cycle rate performance of the composite material; the small diameter of the helical carbon nanofibers also enables the electrolyte to be electrically chargedThe electrode material has better wettability, and the electrolyte can partially enter the inner space of the electrode material, so that the problems of electrode material differentiation, capacity attenuation and the like caused by poor compatibility between the electrode material and the electrolyte can be effectively solved.

3. According to the invention, the spiral carbon nanofibers prepared at a low temperature are carbonized at a temperature of 600-800 ℃, so that the conductivity of the spiral carbon nanofibers can be effectively improved, the surface activity of the spiral carbon nanofibers can be activated, the loading of molybdenum disulfide is facilitated, and the bonding capability with molybdenum disulfide is enhanced. Meanwhile, the invention has low carbonization temperature and short carbonization time, and is beneficial to the load of molybdenum disulfide, thereby being beneficial to improving the electrochemical performance of the composite material.

4. The method adopts the method that the spiral carbon nanofibers are prepared under the low-temperature condition, acetylene in a carbon source gas is subjected to chemical cracking at a lower temperature (260-300 ℃), and the acetylene gas is deposited due to the fact that the acetylene gas does not reach the complete carbonization (cracking) temperature, so that more hydrogen-containing compounds exist in the interior and on the surface of the spiral carbon nanofibers prepared at the low temperature. And the subsequent strong acid is adopted to acidify the spiral carbon nanofibers, so that hydrogen-containing compounds in and on the surfaces of the spiral carbon nanofibers can be effectively removed, the defects of holes are formed on and in the surfaces of the spiral carbon nanofibers, and the quick desorption and storage of sodium ions are facilitated.

In addition, the strong acid is adopted to acidify the spiral carbon nanofibers, functional groups on the surfaces of the spiral carbon nanofibers can be increased, the film forming stability of the spiral carbon nanofibers in the composite material is effectively improved, the high-current charging and discharging are facilitated, the appropriate volume energy density and the coulombic efficiency of the sodium ion battery cathode material are ensured, and the disintercalation of sodium ions in the charging and discharging processes is facilitated, so that the diffusion and migration paths of electrons and ions are shortened, and the electrochemical activity of the composite material is improved.

5. According to the invention, molybdenum disulfide is grafted by adopting a hydrothermal reaction, so that the molybdenum disulfide can grow on the spiral carbon nanofibers in situ, and the molybdenum disulfide and the spiral carbon nanofibers have good binding force, thereby being beneficial to ensuring that the composite material has good electrochemical performance.

Drawings

Fig. 1-XRD pattern of the negative electrode material of sodium ion battery prepared in example 1.

Fig. 2-SEM image of the negative electrode material of sodium ion battery prepared in example 1.

FIG. 3-N-CNF, 1:1.5-CNF/MoS₂、1:2-CNF/MoS₂Cycling performance plot at 100mA/g current density.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Example 1

(1) And (2) placing 0.1g of copper tartrate in a quartz boat, uniformly paving, then placing in a tube furnace, introducing nitrogen, heating to 280 ℃ under the protection of the nitrogen, then stopping introducing the nitrogen, introducing acetylene gas, carrying out heat preservation reaction for 1h, then stopping introducing the acetylene gas, introducing the nitrogen, cooling to room temperature under the protection of the nitrogen, and taking out a sample to obtain the spiral carbon nanofibers.

(2) And (2) placing the spiral carbon nanofibers obtained in the step (1) in a tube furnace, heating to 700 ℃ under the protection of nitrogen, and then carrying out heat preservation reaction for 2 hours to obtain carbonized spiral carbon nanofibers, namely N-CNF.

(3) And (3) acidifying the carbonized spiral carbon nanofibers obtained in the step (2) by using concentrated nitric acid (the concentrated nitric acid completely submerges the carbonized spiral carbon nanofibers), filtering by using a sand core funnel after acidifying for 2 hours, repeatedly washing by using distilled water and ethanol until the solution is neutral, and finally drying in a freeze dryer to obtain the acidified spiral carbon nanofibers, which are marked as CNF.

(4) Accurately weighing 1g of CNF, 1.5g of ammonium molybdate and 10g of thiourea, sequentially adding the CNF, the ammonium molybdate and the thiourea into a beaker, stirring for 1h, then placing the beaker into a reaction kettle, heating to 280 ℃, and preserving heat for 18 h. After cooling, centrifuging for 6 times by using a centrifugal machine until the solution is neutral, drying in a freeze dryer, finally placing in a tubular furnace, heating to 500 ℃ under the protection of nitrogen, and preserving heat for 2 hours to obtain the sodium ion battery cathode material, which is recorded as 1:1.5-CNF/MoS₂。

The true bookExample 1:1.5-CNF/MoS₂The XRD pattern and SEM pattern of (a) are shown in fig. 1 and fig. 2, respectively, where fig. 2 (a) is a pattern enlarged by 100kx and fig. 2 (b) is a pattern enlarged by 150 kx. As can be seen from fig. 1: the four main peaks at 2 θ =14.56 °, 33.07 °, 39.51 ° and 58.29 °, respectively, are attributed to 2H MoS₂(JCPDS number 37-1492) (002), (100), (103) and (110) planes, and no peaks associated with impurities were found, indicating that highly pure MoS was obtained₂(ii) a As can be seen from fig. 2: the spiral carbon nanofibers have smooth surfaces and uniform diameter distribution, and are prepared by a chemical vapor deposition method at a low temperature, so that the spiral carbon nanofibers have a strong micro-spiral structure, the specific surface area of an electrode material is favorably improved, the contact area with electrolyte is increased, electrolyte ions are favorably and fully contacted with the electrode material, the electrolyte ions can be effectively transmitted in the whole electrode, the storage capacity of charges is increased, and the specific capacity of a sodium ion battery is further improved. Petal-shaped MoS growing on spiral carbon nanofiber₂Due to the special three-dimensional spiral structure of the spiral nano carbon fiber, MoS is enabled₂Is wrapped by carbon fiber to prevent MoS₂The dropping and the volume expansion in the charging and discharging process are inhibited, and the electrochemical performance of the sodium ion battery can be further improved.

Example 2

1g of CNF obtained in the step (3) of example 1, 2g of ammonium molybdate and 10g of thiourea were accurately weighed, added to a beaker in sequence, stirred for 1 hour, then placed in a reaction kettle, heated to 280 ℃ and kept warm for 18 hours. After cooling, centrifuging for 6 times by using a centrifugal machine until the solution is neutral, drying in a freeze dryer, finally placing in a tubular furnace, heating to 500 ℃ under the protection of nitrogen, and preserving heat for 3 hours to obtain the sodium ion battery cathode material, which is recorded as 1:2-CNF/MoS₂。

N-CNF、CNF、1:1.5-CNF/MoS₂、1:2-CNF/MoS₂The cycle performance diagram under the current density of 100mA/g is shown in figure 3, and as can be seen from figure 3, the specific capacity of the spiral carbon fiber can be obviously improved through acidification treatment, and MoS grafting is carried out on the spiral carbon fiber₂And the electrode material with high specific capacity and high cycling stability can be obtained. Wherein 1:1.5-CNF/MoS₂Has good cycling stability and specific capacity, and after 90 times of cycling, 344 mAh/g of specific capacity is remained.

Finally, it should be noted that the above-mentioned examples of the present invention are only examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.